How to Tell if Your Air Ducts Are Leaking

Posted Apr 7, 2017

There are lots of ways for your home to lose energy – through leaky door frames, cracks in window trim, loose or missing insulation, etc. A lot of your indoor heating and cooling winds up outdoors and drives up your utility bills.


One part of your home that is susceptible to leaks and energy loss is your ventilation system, typically metal or flexible ductwork. Older homes generally experience more duct leakage because seals and joints may have loosened over the years or may have not been properly connected when they were installed. There are some ways to check and see – or hear – with air duct maintenance in your home are leaking.

The most obvious way to check is by listening. Stand, sit, or kneel close to your ductwork. Listen for any hissing noises when the furnace, air conditioner, or blower motor is in operation. While doing a little air duct cleaning a hissing noise is usually an indication of a leak in a seal or joint. Since ductwork comes in a variety of lengths and contains a number of different connectors, there are likely many joints where pieces have been connected. Some joints are sealed with small sheet metal screws while other joints are sealed with duct tape or mastic. Whatever the connection is, the joints may have come loose over time from vibrations, settling of the home’s foundation, previous repairs, or by someone simply bumping into the ductwork.

Another way to check for a leaking air duct is by looking at insulation which may be wrapped around the ductwork. If an air duct is leaking it will leave dark stains on the insulation over time – giving an exact location of the leak.

Leaks in your air ducts can cause areas like your crawlspace, attic, or garage to be abnormally cold or hot. If you are conditioning unused parts of your home inadvertently, it may be because your ductwork is leaking in those areas.

Finally, a not so easy way to check for leaking ducts is to compare utility bills. If there is a big spike in your heating or cooling costs, it may be because of temperature extremes – but it also may be because your ductwork is leaking. You may not be able to see a big difference in your bills unless there are large leaks or breaks in your ductwork, but keep an eye on your energy costs anyway.

Once you have located any leaks, there are some easy fixes. But you also may want to call your local qualified heating and cooling contractor to perform a whole house energy audit, using leak detection instrumentation to check for leaks. If you have any questions about performing these tasks please contact Milani Plumbing + Draining + Heating.

Milani Blog

Tips, tricks and interesting facts about all things plumbing, drainage, heating & air conditioning from the company you trust. Check back often for new posts!

Featured Blogs

    Recent Blogs

    Proudly Canadian owned and operated 

    Proudly Canadian owned and operated